The present invention relates to improvements in a process and apparatus for the production of a laminated sheath cable composed of a synthetic resin sheath and a cable core with a resin/metal composite laminating tape disposed between the sheath and the core and wound in an overlapping manner along the cable core.
A laminated sheath cable includes, as described above, a cable core, a laminating tape provided around the cable and wound in an overlapping manner along the cable core, and a synthetic resin sheath covering the outside of the laminating tape, which is usually a composite tape composed of a synthetic resin layer and an aluminum or copper layer that are bonded together. Heating at the time of sheath extrusion causes the resin layer to be fused to the sheath, as a result of which the laminating tape is fitted to the inside of the sheath.
FIG. 1 is a schematic illustration of a part of a conventional apparatus for the production of laminated sheath cables of this type. This conventional apparatus for the production of laminated sheath cables includes a cable core feeding reel 2 to feed a cable core 1, a laminating tape feeding pad 4 to feed a laminating tape 3 which is to be longitudinally wrapped on the cable core, a forming unit 5 used to wrap the laminating tape 3 onto the cable core 1 in an overlapping manner, a jig 6 used to prevent bunching of the overlapping portions (not shown) of the laminating tape 3, a squeezing die 7, a heating unit 8 for supplying hot air to render molten and thus fuse the overlapping portions, and pressing rollers 9 and 10 used to press together the overlapping portions which have been heated. These units are disposed in the stated order along the direction in which the cable core 1 moves.
The pressing rollers 9 and 10 are, as can be seen from the enlarged view of FIG. 2, offset from each other in the direction of movement of the core. As a result, forces X and Y are exerted on the cable core 1 at different positions in the lengthwise direction of the cable core 1. In this arrangement, the cable core 1 can readily ride off the rollers 9 and 10, reducing the pressing force used in fusing the overlapping portions of the tape. Consequently, a problem arises in that the overlapping portions cannot be bound together by a sufficiently large pressing force.
FIG. 3 is a partially cut-away cross-sectional view of the pressing rollers 9 and 10 as viewed from the side of the heating unit 8. If the overlapping portion A of the laminating tape 3 is turned to the side as shown in the drawing due to rotation of the cable core 1, the pressing directions X and Y of the pressing rollers 9 and 10 are away from the overlapping portion A. This gives rise to a disadvantage that the force of the pressing rollers 9 and 10 is not exerted efficiently.